1. Field of the Invention
This invention relates in general to a method and system for estimating the life time of a device, and more particularly, to estimation of the life time of a device in a communication system.
2. Description of Related Art
The state of communications technology is currently in flux and subject to rapid and often uncoordinated growth. The ubiquity and diversity of communication devices have placed significant pressure on the providers of communications system infrastructure to accommodate the alarming increase in the number of new users that demand immediate and reliable access to network resources. The rapid development of new and sophisticated software made available to users of such services places additional demands on system infrastructure.
In spite of the rapid and vast development of the communication technology, reliability of devices used in a communication system in practice is still a main concern. Some electronic devices used in the system require a very high reliability. One of the applications of a communication system is a cellular base station. Failures of the electronic devices in the system would directly reduce usability and may cause simultaneous unavailability of a network operation. A typical application of such electronic devices is a base station power amplifier. Accordingly, failure of a base station is undesirable since this would result in unavailability of the network thereby causing, for example, lost revenue to the network provider and serious emergency circumstances where a caller could not report an emergency or request emergency aid.
A high junction temperature is in practice inevitable when there is a need for high power at radio frequencies. However, a decrease in reliability of some electronic devices is often related to operating the devices with a high junction temperature. For example, power amplifiers used in the communication system include semiconductor components such as BJT (Bipolar Junction Transistor) devices, FET (Field Effect Transistor) devices, etc., which have degraded reliability when operating in a high temperature environment with high power levels.
There is no commonly known apparatus and/or method that is capable of predicting a MTTF (Mean Time To Failure) of a device. The MTTF is generally defined as an average time for a hardware breakdown or loss of service. Usually, MTTF calculations use some assumptions based on an average ambient temperature. Also, the ambient temperature is often considered to be evenly distributed. These kinds of methods fail to predict a MTTF in practical applications because they do not take into account the operating temperature of a device, such as the practical junction temperature of a semiconductor device. The practical junction temperature depends, as an example, on the following, but not limited to, factors:
1) Unit or device location in a BTS (Base Transceiver Station) rack: Cooling is not evenly distributed within a BTS cabinet.
2) Type of a BTS rack: Outdoor and indoor cabinets have different properties.
3) BTS location: Geographically hot areas or directly under sun installation have a higher temperature inside the BTS.
4) Ambient temperature variations: Some areas have higher ambient temperature variations than other areas.
5) Used transmitted power: If there is a high incoming power to a device (BJT,FET, etc. . . . ), the device will have a higher junction temperature. On the other hand, a needed output power depends, e.g. in cellular applications, on the size of a cell. The bigger a cell, the more power is needed.
6) Some power amplifier devices are biased such that their DC power usage (at the bias point) and junction temperature depend also on a needed signal power at an output of the devices.
7) The amount of traffic: Because the practical junction temperature depends on the needed output power, the more the traffic in a system, e.g. a time duplexed system (e.g. TDMA, Time Division Multiple Access), the higher the practical junction temperature is.
Accordingly, it can be seen that there is a need for a system and method for following and estimating a life time for high risk devices or components or modules of a system, such as a communication system, such that devices or components or modules in the system can be replaced before they fail.
To overcome the limitations described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention is directed to estimation of a life time of a device.
The present invention provides a system that measures the temperatures of critical components, modules or devices. The system predicts the life time of the device based on the measurements. The system also determines a life time left for a device in a real operational environment.
In one embodiment of the present invention, a system of estimating a life time of a device, includes a temperature sensor, disposed proximate to the device, sensing temperatures of the device at a plurality of time intervals, a memory, coupled to the temperature sensor, recording the sensed temperatures and a controller, coupled to the memory, determining life time points of the device corresponding to the temperatures, calculating accumulated life time points of the device on account for the time intervals to predict the life time of the device.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that for a temperature at an operation time of the device, the controller determines a life time left for the device.
Additional aspect of the present invention is that the life time points corresponding to the temperatures are predetermined, the controller eliminating life time left for the device based upon the life time of the device and the life time points accumulated.
Additional aspect of the present invention is that the device is high power semiconductor.
Additional aspect of the present invention is that the high power semiconductor includes a heat sink, the temperature sensor being mounted on the heat sink of the high power semiconductor.
Additional aspect of the present invention is that the device includes a heat sink, the temperature sensor is mounted on the heat sink.
Additional aspect of the present invention is that the memory includes a database, the database including life time data.
Additional aspect of the present invention is that the life time data is obtained from field tests.
Additional aspect of the present invention is that the memory includes a model for modeling a life time of a device.
Additional aspect of the present invention is that the model and the database are based on real time data collection.
Still another aspect of the invention includes an article of manufacture for a computer-based estimating system for estimating a life time of a device. The article of manufacture includes a computer readable medium having instructions for causing a computer to perform a method, where the method includes sensing a temperature of a device, recording the temperatures of the device at a plurality of time intervals, determining life time points of the device corresponding to the temperatures, calculating accumulated life time points of the device for the time intervals, and predicting a life time for the device based upon the accumulated life time points.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.